1. Field of the Invention
This invention relates generally to methods for the detection and location of leaks in containment facilities such as landfills, surface impoundments, storage tanks, or other like structures. This invention relates more specifically to methods for the detection and location of leaks in geomembrane lined containment facilities and the like, using mise-a-la-masse methods for collecting electrical potential data, mathematical inversion methods for characterizing electrical resistivity, and electrical resistivity tomography (ERT) methods. The methods are applicable to detecting and locating leaks in both newly installed and existing geomembrane lined containments and the like.
2. Description of the Related Art
The primary purpose of geomembrane liners, steel liners, and concrete liners utilized in various types of storage facilities is to provide barriers for liquids contained within the facility in order to prevent the leakage of these liquids into the surrounding environment. The detection and location of leaks in such liners is therefore a critical element in preventing environmental problems such as groundwater pollution and the like. Typical examples of such lined facilities include water reservoirs, surface impoundments, steel tanks, concrete tanks, landfills, leach pads, and other types of liquid and semi-liquid containment facilities. The majority of these facilities, especially those that contain groundwater contaminants, are lined with geomembrane liners.
During geomembrane liner installation the liner is inspected for leaks using visual inspection methods, vacuum box methods, air lance methods, spark testing methods, air pressure testing methods, or other types of well known test methods. These conventional test methods are typically limited to the testing of the liner seam areas. The majority of the liner is, therefore, only visually inspected for leaks.
More recently, electrical leak location methods have been used to detect and locate leaks in geomembrane liners. These electrical methods are capable of testing 100% of the liner area that is covered with water or soil. All of these existing test methods, however, including the electrical methods, require access to the interior of the containment facility by field personnel, or the placement of an electrical wire grid system under or on top of the geomembrane during construction. Electrical leak location methods are the only field proven methods that can locate leaks in a geomembrane liner when soil is placed over the liner. However, even the existing electrical methods require the collection of an array of electrical potential data on the surface of the soil using a close spaced survey grid of some type. A test method is therefore needed that can remotely and automatically detect and locate leaks in both new and existing liners without the need for an extensive survey grid.
U.S. Pat. Nos. 4,543,525; 4,719,407; 4725,785; 4,720,669; 7,751,841; 4,751,467; 4,755,757; and 4,740,757, are all directed to various systems and methods for electrically detecting and locating leaks in geomembrane liners. All of these systems, however, require either the extensive sensor grid structure described above, or require direct access by test operators to the interior liquid or sludge contained in the impoundment. Many of the systems described in these earlier patents involve complex and extensive electrical structures that must often be installed during the installation of the liner.